This invention relates generally to the mining art and, more particularly, to a method and system of hydraulically mining pitched or inclined underground mineral veins, such as coal seams.
A known technique employed in extracting certain unconsolidated ores found in isolated lensatic deposits or pockets is the hydraulic vertical borehole mining process. This process involves predrilling a vertical borehole into the ore formation and lining the borehole with a casing if the overburden is unconsolidated material. A mining tool is then inserted through the borehole and serves to disintegrate the ore by jetting a fluid, usually water, into the ore formation. The liquid containing the removed ore in suspension forms a slurry which is pumped upwardly through the borehole to the ground surface. While this process admirably serves its intended purpose for recovering ore from isolated underground pockets, it has not proven economically feasible in mining continuous underground mineral veins, such as coal seams for example.
Conventional coal mining is invariably performed in near-level coal seams. Pitched coal seams, i.e., seams that extend downwardly at an angle from a true horizontal, generally have been avoided because of the excessive cost incurred in recovering the coal. As a result, hundreds of millions of tons of coal reserves remain buried in these pitched coal seams.
Some pitched coal seams are currently being mined by the wellknown technique of strip mining until the cost of removing the overburden becomes prohibitive. In some instances, further recovery of strip mined coal is achieved by employing augers which drill down the dip of the pitched seam. However, the augering method has a limitation of several hundred feet, thereby leaving behind reserves of unmined coal. In either event, this strip mining technique involves extensive surface disruption creating safety hazards and environmental problems, as well as adversely affecting local ground water and surface streams. Moreover, the accumulation and disposal of overburden wastes poses ecological and economic problems. Consequently, most pitched coal seams have never been mined except for scavenging along the outcrop.
Accordingly, it is a primary object of the present invention to provide a new and useful method of hydraulically mining underground pitched mineral veins extending downwardly at an angle relative to a true horizontal.
It is another object of this invention to provide a method of hydraulically mining pitched mineral veins while minimizing surface disruption and the accumulation of shale and rock wastes on the surface of the earth.
It is a further object of the present invention to provide an improved hydraulic mining method avoiding damage to ground water quality and hydrology and avoiding surface water pollution.
These and other objects, advantages, and characterizing features of this invention will become apparent from the ensuing detailed description of an illustrative embodiment thereof, when taken together with the accompanying drawings wherein like reference characters denote like parts throughout the various views.